The present invention relates generally to a method of controlling a ribbon motor for a color printing system. More particularly, it relates to a method of controlling the operation of a ribbon motor for a color printing system whereby a ribbon travels in reverse by one color pitch when the time that the printer is in a standby mode exceeds a prescribed critical time after the last printing operation so that the ribbon's region used for the next printing is free from dust.
A ribbon driving control portion of a conventional sublimation-type thermal printing system may be divided into four blocks: a color detector 106; a central processing unit CPU 107; a ribbon motor driving controller 108; and a ribbon motor 109, as shown in FIG. 1.
Once the printing operation starts, the CPU 107 controls the ribbon motor driving controller 108 to make a ribbon 102 travel until the color detector 106 detects yellow. When the color detector 106 detects yellow, a thermal print head 103 (TPH) is pressed onto the ribbon 102 and paper 101 and generates heat to output a corresponding image on the paper 101.
Once the "yellow" printing operation is completed, the CPU 107 returns the TPH 103 to its original position, and makes the ribbon 102 travel until the color detector 106 detects the next color, magenta. When the color detector 106 detects magenta, the TPH 103 is pressed onto the ribbon 102 and paper 101 to imprint data corresponding to the color on the paper 101. The above-described process is executed with respect to the printing of data corresponding to the colors of yellow, magenta, cyan and black.
FIG. 2 illustrates a ribbon used for a sublimation-type printing system. If three- or four-color printing operation is performed, the conventional ribbon motor driving controller 108 holds the ribbon ready until there is a command to print. If a long period of time elapses after printing, dust particles may lay on the surface of the ribbon, and when the printing operation is reinitiated, the dust on the ribbon is transferred to paper along with the color from the ribbon, thereby reducing the print quality.
As shown in FIG. 3, after the printing operation (in the case of the three- or four-color ribbon), the end of the ribbon's cyan/black section (the last printing color) is placed right under the TPH 103, and the dust adversely affects a region A of the ribbon so that dust particulates on the ribbon's yellow section negatively affect a region B of the ribbon during subsequent printing to thereby deteriorate the print quality. As described above, in such a sublimation-type thermal printing system, the dust on the ribbon and paper surface may deteriorate the print quality, and it is necessary to avoid the waste of ribbons and paper due to poor print quality by providing higher standards of print quality, reliability, and performance. As a long period of time elapses after printing, dust may lay on the surface of the ribbon and cause this poor print quality.